From Tapestries MUCK
A Trigger object is the object that the MPI script is evaluated from.
A List is a string containing several individual substring items, seperated by carriage return characters.
A property based list is a set of consecutively numbered properties that each contain one string in a list of strings. Property based lists are often numbered like: listname1, listname2, listname3, listname4, &c. Another popular format is listname#/1, listname#/2, listname#/3, etc. MPI can read in either of those formats, and several more, for that matter.
For logical constructs, a string value of "0", or a null string ("") are both considered false. Any other value is considered true.